Chapter 4 - Magnetostrictive Material and Actuator Characterization

Abstract

Publisher Summary Low-frequency magnetostrictive material and actuator characterization are best for time domain methods. The high strains that can be achieved with magnetostrictive materials compared to piezoelectric materials make them more fit for low-frequency applications in which higher strains are needed. The usable frequency range of highly magnetostrictive materials has extended toward higher frequencies because of improved technology regarding eddy current prevention measures, such as lamination and powder technology combined with an increased demand for high-power, high-frequency actuators. Therefore, both magnetostrictive material and actuator characterization comprise the traditional methods for characterizing high-frequency piezoelectric actuators and low-frequency characterization methods. The low-frequency magnetostrictive actuators are often used in nonresonant applications for control purposes. The excitation levels are comparatively high, which together with the off-resonance operation mode, imply a nonlinear and hysteretic material behavior. It can be concluded that all dissipative phenomena, such as eddy currents, hysteresis, and material damping, for a studied resonance are included in the efficiency estimations. The effect of various actuator designs can be studied with the electric-impedance method by examining the input actuator voltage and current. This makes the method very popular among magnetostrictive actuator designers, even though the developed actuators show a significant nonlinear and/or hysteretic behavior.